＂Intelligent＂ reforming catalysts： Trace noble metal-doped Ni/Mg（A1）O derived from hydrotalcites

Trace amounts of noble metal-doped Ni/Mg(Al)O catalysts were prepared starting from Mg-Al hydrotalcites (HTs) and tested in daily start-up and shut-down (DSS) operation of steam reforming (SR) of methane or partial oxidation (PO) of propane. Although Ni/Mg(Al)O catalysts prepared from Mg(Ni)-Al HT exhibited high and stable activity in stationary SR, PO and dry reforming of methane and propane, the Ni/Mg(Al)O catalysts were drastically deactivated due to Ni oxidation by steam as purge gas when they were applied in DSS SR ofmethane. Such deactivation was effectively suppressed by doping trace amounts of noble metal on the catalysts by using a “memory effect” of HTs. Moreover, the noble metal-doped Ni/Mg(Al)O catalysts exhibited “intelligent” catalytic behaviors, i.e., self-activation and self-regenerative activity, leading to high and sustainable activity during DSS operation. Pt was the most effective among noble metals tested. The self-activation occurred by the reduction of Ni2+ in Mg(Ni,Al)O periclase to Ni0 assisted by hydrogen spillover from Pt (or Pt-Ni alloy). The self-regenerative activity was accomplished by self-redispersion of active Ni0 particles due to a reversible reductionoxidation movement of Ni between the outside and the inside of the Mg(Al)O periclase crystal; surface Ni0 was oxidized to Ni2+ by steam and incorporated into Mg(Ni2+,Al)O periclase, whereas the Ni2+ in the periclase was reduced to Ni0 by the hydrogen spillover and appeared as the fine Ni0 particles on the catalyst surface. Further a “green” preparation of the Pt/Ni/Mg3.5Al]O catalysts was accomplished starting from commercial Mg3.5-Al HT by calcination, followed by sequential impregnation of Ni and Pt.

Intelligent reforming catalysts: Trace noble metal-doped Ni/Mg(Al)O derived from hydrotalcites (Special column of methane transformation, Review)

Trace amounts of noble metal-doped Ni/Mg(Al)O catalysts were prepared starting from Mg-Al hydrotalcites (HTs) and tested in daily start-up and shut-down (DSS) operation of steam reforming (SR) of methane or partial oxidation (PO) of propane. Although Ni/Mg(Al)O catalysts prepared from Mg(Ni)-Al HT exhibited high and stable activity in stationary SR, PO and dry reforming of methane and propane, the Ni/Mg(Al)O catalysts were drastically deactivated due to Ni oxidation by steam as purge gas when they were applied in DSS SR of methane. Such deactivation was effectively suppressed by doping trace amounts of noble metal on the catalysts by using a “memory effect” of HTs. Moreover, the noble metal-doped Ni/Mg(Al)O catalysts exhibited “intelligent” catalytic behaviors, i.e., self-activation and self-regenerative activity, leading to high and sustainable activity during DSS operation. Pt was the most effective among noble metals tested. The self-activation occurred by the reduction of Ni²⁺ in Mg(Ni, Al)O periclase to Ni⁰ assisted by hydrogen spillover from Pt (or Pt-Ni alloy). The self-regenerative activity was accomplished by self-redispersion of active Ni⁰ particles due to a reversible reduction- oxidation movement of Ni between the outside and the inside of the Mg(Al)O periclase crystal; surface Ni⁰ was oxidized to Ni²⁺ by steam and incorporated into Mg(Ni²⁺,Al)O periclase, whereas the Ni²⁺ in the periclase was reduced to Ni⁰ by the hydrogen spillover and appeared as the fine Ni⁰ particles on the catalyst surface. Further a “green” preparation of the Pt/Ni/Mg_3.5Al]O catalysts was accomplished starting from commercial Mg_3.5-Al HT by calcination, followed by sequential impregnation of Ni and Pt.